Oil pollution doesn't have to kill fish to have a long-term impact, according to a recent study in the Proceedings of the National Academy of Sciences (PNAS). Researchers found that Gulf killifish (Fundulus grandis) that had been exposed to very low to non-detectable levels of oil contamination from the Deepwater oil spill last year, still showed developmental problems that are likely to impact fish populations for decades to come.

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"Though the fish may be 'safe to eat' based on low chemical burdens in their tissues, that doesn't mean that the fish are healthy or that the fish are capable of reproducing normally," explains Andrew Whitehead with Louisiana State University.

Whitehead and colleagues measured water contamination and took tissue samples from Gulf killifish and spawning marshes three times following the Deepwater spill. While the water showed little to no contamination, the fish's tissue revealed another story. The liver showed responses connected to developmental abnormalities that likely impaired the fish's ability to reproduce successfully. Gill tissues showed stress linked to oil exposure, which didn't go away even after the little recorded oil did. As an important prey species, Gulf killifish provide food to a host of other Gulf marine organisms, including the commercially sought-after red snapper.

"Early life-stages of many organisms are particularly sensitive to the toxic effects of oil and because marsh contamination occurred during the spawning season of many important species," Whitehead says.